Resin composition for printed wiring board material and prepreg, resin sheet, metal foil-clad laminate, and printed wiring board using the same

ABSTRACT

A resin composition used as a material of an insulating layer of a printed wiring board including the insulating layer and a conductor layer formed on a surface of the insulating layer by plating, the resin composition including: an epoxy compound; a cyanate compound; a maleimide compound; an inorganic filler; and an imidazole silane, wherein the maleimide compound includes a predetermined maleimide compound, a content of the maleimide compound is 25% by mass or less based on 100% by mass of a total content of the epoxy compound, the cyanate compound, and the maleimide compound, and the imidazole silane includes a compound represented by the formula (3).

TECHNICAL FIELD

The present invention relates to a resin composition useful as amaterial of the insulating layer of a printed wiring board, and aprepreg, a resin sheet, a metal foil-clad laminate, and a printed wiringboard using such a resin composition.

BACKGROUND ART

In recent years, the miniaturization and performance enhancement ofelectronic equipment have advanced. For multilayer printed wiringboards, in order to improve the packaging density of electroniccomponents, conductor wiring is increasingly made finer, and theirwiring formation techniques are desired. As methods for forming highdensity fine wiring on an insulating layer, an additive method in whicha conductor layer is formed only by electroless plating, a semi-additivemethod in which a thin copper layer is formed on the entire surface byelectroless plating, and then a conductor layer is formed byelectrolytic plating, and then the thin copper layer is flash-etched,and the like are known.

In addition, due to the miniaturization and densification of multilayerprinted wiring boards, thinning laminates used for multilayer printedwiring boards is actively studied. With thinning, the problems of adecrease in packaging reliability and an increase in the warpage ofmultilayer printed wiring boards occur, and therefore high adhesivenessand high glass transition temperature are require of resin compositionsthat are materials of insulating layers.

Patent Literatures 1 and 2 describe techniques using an epoxy resin, aphenolic resin, and an imidazole silane in order to improve theadhesiveness between an inner layer circuit and an insulating layer andmoldability.

In addition, Patent Literature 3 describes a resin composition using anepoxy resin, a curing agent, silica, and an imidazole silane anddiscloses that when this resin composition is cured, and a metal layeris formed, by plating treatment, on the surface of the cured productsubsequently subjected to roughening treatment, the cured product andthe metal layer exhibit high adhesion.

CITATION LIST Patent Literature Patent Literature 1: Japanese PatentLaid-Open No. 2003-318499 Patent Literature 2: Japanese Patent No.4016782 Patent Literature 3: Japanese Patent No. 4686750 SUMMARY OFINVENTION Technical Problem

However, Patent Literatures 1 and 2 describe the adhesion between aninner layer circuit and an insulating layer but do not describe at allthe concepts of the adhesiveness between a conductor layer formed byplating and an insulating layer and high glass transition temperature.

In addition, the cured product described in Patent Literature 3 hasexcellent adhesive force between the plating metal layer on the curedproduct and the cured product but is not satisfactory from the viewpointof the glass transition temperature required as the insulating layer ofa printed wiring board.

The present invention has been made in view of the above problems, andit is an object of the present invention to provide a resin compositionthat has excellent prepreg productivity, excellent adhesiveness betweenan insulating layer and a conductor layer formed on the surface of theinsulating layer by plating, high glass transition temperature, and alsoexcellent heat resistance after moisture absorption when used as amaterial of the insulating layer of a printed wiring board, and providea prepreg, a resin sheet, a metal foil-clad laminate, and a printedwiring board using such a resin composition.

Solution to Problem

The present inventors have obtained the finding that in a resincomposition comprising an epoxy compound, a cyanate compound, amaleimide compound, an inorganic filler, and an imidazole silane,selecting the maleimide compound and the imidazole silane fromparticular types and setting the ratio of the maleimide compound to thetotal content of the epoxy compound, the cyanate compound, and themaleimide compound in a particular range provide a resin compositionthat has excellent adhesiveness between an insulating layer and aconductor layer formed on the surface of the insulating layer byplating, high glass transition temperature, excellent prepregproductivity, and also excellent heat resistance after moistureabsorption when used as a material of the insulating layer of a printedwiring board. The present invention is based on such a finding.

Specifically, the present invention is as follows.

[1]

A resin composition used as a material of an insulating layer of aprinted wiring board comprising the insulating layer and a conductorlayer formed on a surface of the insulating layer by plating, the resincomposition comprising:

an epoxy compound (A); a cyanate compound (B); a maleimide compound (C);an inorganic filler (D); and an imidazole silane (E), wherein

the maleimide compound (C) comprises a maleimide compound represented bythe following formula (1) and/or a maleimide compound represented by thefollowing formula (2),

a content of the maleimide compound (C) is 25% by mass or less based on100% by mass of a total content of the epoxy compound (A), the cyanatecompound (B), and the maleimide compound (C),

and the imidazole silane (E) comprises a compound represented by thefollowing formula (3),

wherein n is a real number in a range of 1 to 30 as an average value,

wherein R¹, R², R³, and R⁴ each independently represent a hydrogen atomor a methyl group, and n is a real number in a range of 1 to 10 as anaverage value,

wherein R⁵ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R⁶ represents hydrogen, a vinyl group, or an alkyl group having 1to 5 carbon atoms, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 3 carbon atoms, X represents an acetate ion or a phthalateion, Y represents hydrogen or a hydroxyl group, and n represents aninteger of 1 to 3.[2]

The resin composition according to the previous section [1], wherein thecyanate compound (B) comprises a naphthol aralkyl-based cyanate compoundrepresented by the following formula (4) and/or a novolac-based cyanatecompound represented by the following formula (5),

wherein R⁹, R¹⁰, R¹¹, and R¹² each independently represent a hydrogenatom or a methyl group, and n represents an integer of 1 or more,

wherein R¹³, R¹⁴, R¹⁵, and R¹⁶ each independently represent a hydrogenatom or a methyl group, and n represents an integer of 1 or more.[3]

The resin composition according to the previous section [1] or [2],wherein the inorganic filler (D) comprises at least one or more selectedfrom the group consisting of silica, aluminum hydroxide, alumina,boehmite, magnesium oxide, and magnesium hydroxide.

[4]

The resin composition according to any one of the previous sections [1]to [3], wherein a content of the epoxy compound (A) is 40 to 75% by massbased on 100% by mass of the total content of the epoxy compound (A),the cyanate compound (B), and the maleimide compound (C).

[5]

The resin composition according to any one of the previous sections [1]to [4], wherein a content of the cyanate compound (B) is 20 to 40% bymass based on 100% by mass of the total content of the epoxy compound(A), the cyanate compound (B), and the maleimide compound (C).

[6]

The resin composition according to any one of the previous sections [1]to [5], wherein a content of the inorganic filler (D) is 50 to 300% bymass based on 100% by mass of the total content of the epoxy compound(A), the cyanate compound (B), and the maleimide compound (C).

[7]

The resin composition according to any one of the previous sections [1]to [6], wherein a content of the imidazole silane (E) is 0.1 to 3% bymass based on 100% by mass of the total content of the epoxy compound(A), the cyanate compound (B), and the maleimide compound (C).

[8]

A prepreg comprising a substrate and the resin composition according toany one of the previous sections [1] to [7] with which the substrate isimpregnated.

[9]

A resin sheet comprising an outer layer comprising metal foil or a metalfilm, and a layer comprising the resin composition according to any oneof the previous sections [1] to [7] laminated on the outer layer.

[10]

A metal foil-clad laminate comprising the prepreg according to theprevious section [8] and metal foil laminated on one surface or bothsurfaces of the prepreg.

[11]

The metal foil-clad laminate according to the previous section [10],wherein the metal foil has a matte surface having a surface roughness Rzof 0.7 μm to 2.5 μm.

[12]

A printed wiring board made using the prepreg according to the previoussection [8] as a buildup material.

[13]

A printed wiring board made using the resin sheet according to theprevious section [9] as a buildup material.

[14]

The printed wiring board according to the previous section [13] made bysurface-treating the resin sheet and forming a pattern by plating.

[15]

A printed wiring board made using the metal foil-clad laminate accordingto the previous section [10] as a buildup material.

[16]

The printed wiring board according to the previous section [15] made byetching the metal foil of the metal foil-clad laminate, performingsurface treatment, and forming a pattern by plating.

[17]

A printed wiring board comprising an insulating layer and a conductorlayer formed on a surface of the insulating layer, wherein

the insulating layer comprises the resin composition according to anyone of the previous sections [1] to [7].

Advantageous Effects of Invention

The resin composition of the present invention exhibits at least any,preferably all, of the following effects of (1) to (4).

(1) The prepreg productivity is excellent.(2) The adhesiveness between an insulating layer and a conductor layerformed on the surface of the insulating layer by plating is excellent.(3) The glass transition temperature is high.(4) The heat resistance after moisture absorption is excellent.

DESCRIPTION OF EMBODIMENT

A mode for carrying out the present invention (hereinafter referred toas “this embodiment”) will be described in detail below, but the presentinvention is not limited to this, and various modifications can be madewithout departing from the spirit thereof.

[I. Resin Composition]

A resin composition in this embodiment is

a resin composition used as a material of the insulating layer of aprinted wiring board comprising the insulating layer and a conductorlayer formed on the surface of the insulating layer by plating, theresin composition comprising:

an epoxy compound (A); a cyanate compound (B); a maleimide compound (C);an inorganic filler (D); and an imidazole silane (E), wherein

the maleimide compound (C) comprises a compound represented by thefollowing formula (1) and/or a compound represented by the followingformula (2),

the content of the maleimide compound (C) is 25% by mass or less basedon 100% by mass of the total content of the epoxy compound (A), thecyanate compound (B), and the maleimide compound (C),

and the imidazole silane (E) comprises a compound represented by thefollowing formula (3),

wherein n is a real number in the range of 1 to 30 as an average value,

wherein R¹, R², R³, and R⁴ each independently represent a hydrogen atomor a methyl group, and n is a real number in the range of 1 to 10 as anaverage value,

wherein R⁵ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R⁶ represents hydrogen, a vinyl group, or an alkyl group having 1to 5 carbon atoms, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 3 carbon atoms, X represents an acetate ion or a phthalateion, Y represents hydrogen or a hydroxyl group, and n represents aninteger of 1 to 3.

The resin composition in this embodiment is used as a material of theinsulating layer of a printed wiring board comprising the insulatinglayer and a conductor layer formed on the surface of the insulatinglayer by plating and, more specifically, is preferably used as amaterial of the insulating layer of a printed wiring board comprisingthe insulating layer and a conductor layer formed by selectively platingthe surface of the insulating layer by a semi-additive method or a fulladditive method. The insulating layer comprising the resin compositionin this embodiment has excellent adhesiveness to a conductor layerformed on the surface of the insulating layer by plating and thereforeis particularly suitable for such an application.

[I-1. Epoxy Compound (A)]

The epoxy compound (A) contained in the resin composition in thisembodiment is an organic compound having at least one epoxy group. Thenumber of epoxy groups per molecule of the epoxy compound (A) is 1 ormore. The number of epoxy groups is more preferably 2 or more.

The epoxy compound (A) is not particularly limited, and conventionallyknown epoxy resins can be used. Examples thereof include biphenylaralkyl-based epoxy compounds (epoxy group-containing biphenyl aralkylresins), naphthalene-based epoxy compounds (epoxy group-containingcompounds having a naphthalene skeleton: naphthalene bifunctional-basedepoxy compounds), bisnaphthalene-based epoxy compounds (epoxygroup-containing compounds having a bisnaphthalene skeleton: naphthalenetetrafunctional-based epoxy compounds), polyfunctional phenol-basedepoxy resins, naphthylene ether-based epoxy resins, phenol aralkyl-basedepoxy resins, phenol novolac-based epoxy resins, cresol novolac-basedepoxy resins, xylene novolac-based epoxy resins, naphthaleneskeleton-modified novolac-based epoxy resins, dicyclopentadienenovolac-based epoxy resins, biphenyl novolac-based epoxy resins, phenolaralkyl novolac-based epoxy resins, naphthol aralkyl novolac-based epoxyresins, aralkyl novolac-based epoxy resins, aromatic hydrocarbonformaldehyde-based epoxy compounds (epoxy group-containing aromatichydrocarbon formaldehyde resins), anthraquinone-based epoxy compounds(epoxy group-containing compounds having an anthraquinone skeleton),anthracene-based epoxy resins, naphthol aralkyl-based epoxy compounds(epoxy group-containing naphthol aralkyl resins),dicyclopentadiene-based epoxy resins, Xylok-based epoxy compounds (epoxygroup-containing Xylok resins), bisphenol A-based epoxy resins,bisphenol E-based epoxy resins, bisphenol F-based epoxy resins,bisphenol S-based epoxy resins, bisphenol A novolac-based epoxy resins,trifunctional phenol-based epoxy compounds (epoxy group-containingcompounds having a trifunctional phenol skeleton), tetrafunctionalphenol-based epoxy compounds (epoxy group-containing compounds having atetrafunctional phenol skeleton), biphenyl-based epoxy resins (epoxygroup-containing compounds having a biphenyl skeleton), aralkylnovolac-based epoxy resins, triazine skeleton epoxy compounds (triazineskeleton-containing epoxy resins), triglycidyl isocyanurate, alicyclicepoxy resins, polyol-based epoxy resins, glycidyl amine, glycidyl-basedester resins, compounds obtained by epoxidizing the double bond of adouble bond-containing compound such as butadiene, and compoundsobtained by the reaction of a hydroxyl group-containing silicone resinand epichlorohydrin.

As described in the above illustration, an epoxy compound having astructure obtained by epoxidizing a certain resin or compound may berepresented herein with the description “ . . . -based epoxy compound”attached to the name of the resin or compound.

Among these, the epoxy compound (A) is preferably one or two or moreselected from the group consisting of biphenyl aralkyl-based epoxycompounds, naphthalene-based epoxy compounds, bisnaphthalene-based epoxycompounds, aromatic hydrocarbon formaldehyde-based epoxy compounds,anthraquinone-based epoxy compounds, naphthol aralkyl-based epoxycompounds, and Xylok-based epoxy compounds from the viewpoint ofimproving the adhesiveness between the insulating layer and the platingconductor layer, flame retardancy, and the like. Preferred examples ofthe aromatic hydrocarbon formaldehyde-based epoxy compounds includecompounds obtained by modifying with a hydroxyl group-containingaromatic hydrocarbon such as phenol or xylenol an aromatic hydrocarbonformaldehyde resin obtained by polymerizing an aromatic hydrocarbon suchas benzene, toluene, or xylene with formaldehyde, and furtherepoxidizing the hydroxyl group, and compounds obtained by epoxidizingthe hydroxyl group of an aromatic hydrocarbon formaldehyde resinobtained by polymerizing a hydroxyl group-containing aromatichydrocarbon such as phenol or xylenol with formaldehyde.

Further, from the viewpoint of still further lowering the thermalexpansion coefficient of the resin composition, the epoxy compound (A)is preferably one or two or more selected from the group consisting ofbiphenyl aralkyl-based epoxy resins, naphthalene-based epoxy compounds,bisnaphthalene-based epoxy compounds, and anthraquinone-based epoxycompounds.

The biphenyl aralkyl-based epoxy compounds are not particularly limited,but, for example, a compound represented by the following formula (6) ispreferred. By using such a biphenyl aralkyl-based epoxy resin, thecombustion resistance of the resin composition tends to be furtherimproved.

wherein n represents an integer of 1 or more; and the upper limit valueof n is generally 10, preferably 7.

The content of the epoxy compound (A) is not particularly limited but ispreferably 40 to 75% by mass, more preferably 50 to 70% by mass, andfurther preferably 60 to 70% by mass based on 100% by mass of the totalcontent of the epoxy compound (A), the cyanate compound (B), and themaleimide compound (C) from the viewpoint of providing high glasstransition temperature and good heat resistance to the insulating layerwhile maintaining the adhesiveness between the insulating layer and theplating conductor layer. When two or more epoxy compounds (A) are usedtogether, the total content of these preferably satisfies the abovevalues.

One epoxy compound (A) may be used alone, or two or more epoxy compounds(A) may be used together in any combination and ratio.

As the epoxy compound (A), ready-made products having various structuresare commercially available, and they can be appropriately obtained andused. In addition, the epoxy compound (A) may be produced using avariety of known production methods. Such production methods are notparticularly limited. Examples thereof include a method of obtaining orsynthesizing a hydroxyl group-containing compound having the desiredskeleton, and modifying the hydroxyl group by a known method forepoxidation (epoxy group introduction).

[I-2. Cyanate Compound (B)]

The cyanate compound (B) contained in the resin composition in thisembodiment is a compound having a cyanato group (cyanate group). Byusing the cyanate compound (B), excellent properties such as chemicalresistance, high glass transition temperature, and low thermal expansionproperties can be provided to the resin composition.

The cyanate compound (B) is not particularly limited, and conventionallyknown epoxy resins can be used. Examples thereof include one or moreselected from the group consisting of naphthol aralkyl-based cyanatecompounds (cyanato group-containing naphthol aralkyl resins),novolac-based cyanate compounds (cyanato group-containing novolacresins), aromatic hydrocarbon formaldehyde-based cyanate compounds(cyanato group-containing aromatic hydrocarbon formaldehyde resins), andbiphenyl aralkyl-based cyanate compounds (cyanato group-containingbiphenyl aralkyl resins).

As described in the above illustration, the cyanate compound (B) havinga structure obtained by converting a certain resin or compound into acyanato (cyanate) may be represented herein with the description “ . . .-based cyanate compound” attached to the name of the resin or compound.

Among these, as the cyanate compound (B), one or two or more selectedfrom the group consisting of naphthol aralkyl-based cyanate compounds,novolac-based cyanate compounds, aromatic hydrocarbon formaldehyde-basedcyanate compounds, and biphenyl aralkyl-based cyanate compounds areparticularly preferred from the viewpoint of providing a resincomposition which has excellent flame retardancy and high curability andin which the obtained cured product has high glass transitiontemperature. The aromatic hydrocarbon formaldehyde-based cyanatecompounds are not particularly limited. Examples thereof includecompounds obtained by a method of polymerizing an aromatic hydrocarbonsuch as benzene, toluene, or xylene with formaldehyde to obtain anaromatic hydrocarbon formaldehyde resin, modifying the obtained aromatichydrocarbon formaldehyde resin with a hydroxyl group-containing aromatichydrocarbon such as phenol or xylenol, and further converting thehydroxyl group into a cyanato, a method of polymerizing a hydroxylgroup-containing aromatic hydrocarbon such as phenol or xylenol withformaldehyde to obtain a hydroxyl group-containing aromatic hydrocarbonformaldehyde resin, and converting the hydroxyl group of the obtainedhydroxyl group-containing aromatic hydrocarbon formaldehyde resin into acyanato, or the like.

Further, among these, naphthol aralkyl-based cyanate compounds and/ornovolac-based cyanate compounds are preferred. By using naphtholaralkyl-based cyanate compounds, the curability of the resin compositiontends to be still further improved, and a cured product having betterflame resistance tends to be able to be obtained. In addition, by usingnovolac-based cyanate compounds, the heat resistance and the flameresistance tend to be further improved.

The above naphthol aralkyl-based cyanate compounds are not particularlylimited, but, for example, a compound represented by the followingformula (4) is preferred.

In the above formula (4), R⁹, R¹⁰, R¹¹, and R¹² each independentlyrepresent a hydrogen atom or a methyl group, and among these, a hydrogenatom is preferred. In addition, in the above formula (4), n representsan integer of 1 or more. The upper limit value of n is preferably 10,more preferably 6.

In addition, the novolac-based cyanate compounds are not particularlylimited, but, for example, a compound represented by the followingformula (5) is preferred.

In the above formula (5), R¹³, R¹⁴, R¹⁵, and R¹⁶ each independentlyrepresent a hydrogen atom or a methyl group, and among these, a hydrogenatom is preferred. In addition, in the above formula (5), n representsan integer of 1 or more. The upper limit value of n is preferably 10,more preferably 7.

The content of the cyanate compound (B) in the resin composition is notparticularly limited but is preferably 20 to 40% by mass, morepreferably 20 to 35% by mass, based on 100% by mass of the total contentof the epoxy compound (A), the cyanate compound (B), and the maleimidecompound (C) from the viewpoint of providing high glass transitiontemperature and good heat resistance to the insulating layer. When twoor more cyanate compounds (B) are used together, the total content ofthese preferably satisfies the above ratios.

In the resin composition in this embodiment, one cyanate compound (B)may be used alone, or two or more cyanate compounds (B) may be usedtogether in any combination and ratio. In addition, one or two or moreknown cyanate compounds other than the above-described cyanate compound(B) can also be used together.

As the cyanate compound (B), ready-made products having variousstructures are commercially available, and they can be appropriatelyobtained and used. In addition, the cyanate compound (B) may be producedusing a variety of known production methods. Such production methods arenot particularly limited. Examples thereof include a method of obtainingor synthesizing a hydroxyl group-containing compound having the desiredskeleton, and modifying the hydroxyl group by a known method forconversion into a cyanato. The method for converting a hydroxyl groupinto a cyanato is not particularly limited. Examples thereof include amethod described in Ian Hamerton, “Chemistry and Technology of CyanateEster Resins,” Blackie Academic & Professional.

[I-3. Maleimide Compound (C)]

The maleimide compound (C) contained in the resin composition in thisembodiment comprises a maleimide compound represented by the followingformula (1) and/or a maleimide compound represented by formula (2), andprepolymers of these maleimide compounds, prepolymers of these maleimidecompounds and amine compounds, and the like can also be used. By usingthe maleimide compound represented by the following formula (1), heatresistance can be provided to the insulating layer while theadhesiveness between the insulating layer and the plating conductorlayer is maintained. In addition, by using the maleimide compoundrepresented by the following formula (2), high glass transitiontemperature can be provided while the adhesiveness between theinsulating layer and the plating conductor layer is maintained.

wherein n is a real number in the range of 1 to 30 as an average value.

wherein R¹, R², R³, and R⁴ each independently represent a hydrogen atomor a methyl group, and n is a real number in the range of 1 to 10 as anaverage value.

The maleimide compound (C) represented by the above formula (1) is{polytetramethylene oxide-bis(4-maleimidobenzoate)}, and one or two ormore maleimide compounds having different n represented by the aboveformula (1) can also be appropriately mixed and used. The maleimidecompound (C) represented by the above formula (1) can be obtained byreacting a diamino compound represented by the following formula (7){polytetramethylene oxide-bis(4-aminobenzoate)} with maleic anhydride.The molecular weight of the diamino compound represented by thefollowing formula (7) usually reflects a molecular weight distributionderived from polytetramethylene glycol, a raw material, and thereforethe maleimide compound (C) represented by the above formula (1) has amolecular weight distribution in a predetermined range in most cases.

wherein n is a real number in the range of 1 to 30 as an average value.

In the above formulas (1) and (7), n is a real number in the range of 1to 30, preferably a real number in the range of 3 to 21, and morepreferably a real number in the range of 7 to 18 as an average value.

Examples of products of the maleimide compound (C) represented byformula (1) include “BMI-650P” and “BMI-1000P” manufactured by K.IChemical Industry Co., Ltd. Examples of products of the maleimidecompound (C) represented by formula (2) include “BMI-2300” manufacturedby Daiwa Fine Chemicals Co., Ltd.

The content of the maleimide compound (C) is 25% by mass or less,preferably 0.10 to 25% by mass, and more preferably 3.0 to 20% by massbased on 100% by mass of the total content of the epoxy compound (A),the cyanate compound (B), and the maleimide compound (C). When thecontent of the maleimide compound (C) is 25% by mass or less, theinteraction between the components of the resin composition,particularly the cyanate compound (B) and the particular imidazolesilane (E), is further improved, and the glass transition temperature Tgof the insulating layer can also be maintained at an extremely highvalue (for example, 230° C. or more) while the adhesiveness between theinsulating layer formed using the resin composition and the platingconductor layer is significantly improved. Thus, according to the resincomposition in this embodiment, the unpredictable significant effect ofachieving both excellent adhesiveness and high heat resistance at highlevels can be obtained.

In the resin composition in this embodiment, one maleimide compound (C)may be used alone, or two or more maleimide compounds (C) may be usedtogether in any combination and ratio. When two or more maleimidecompounds (C) are used together, the total content of these preferablysatisfies the above ratios.

[I-4. Inorganic Filler (D)]

The inorganic filler (D) contained in the resin composition in thisembodiment is not particularly limited. Examples thereof include kaolin,calcined kaolin, calcined clay, uncalcined clay, silica (for example,natural silica, fused silica, amorphous silica, hollow silica, wetsilica, synthetic silica, and Aerosil), aluminum compounds (for example,boehmite, aluminum hydroxide, alumina, hydrotalcite, aluminum borate,and aluminum nitride), magnesium compounds (for example, magnesiumcarbonate, magnesium oxide, and magnesium hydroxide), calcium compounds(for example, calcium carbonate, calcium hydroxide, calcium sulfate,calcium sulfite, and calcium borate), molybdenum compounds (for example,molybdenum oxide and zinc molybdate), talc (for example, natural talcand calcined talc), mica (isinglass), glass (for example, short fibrousglass, spherical glass, fine powder glass, and hollow glass such as Aglass, NE glass, C glass, L glass, S glass, M glass G20, E glass, Tglass, D glass, S glass, and Q glass), titanium oxide, zinc oxide,zirconium oxide, barium sulfate, zinc borate, barium metaborate, sodiumborate, boron nitride, aggregated boron nitride, silicon nitride, carbonnitride, strontium titanate, barium titanate, stannates such as zincstannate, and rubber-based fillers (for example, rubber powders such asstyrene-based rubber powders, butadiene-based rubber powders, andacrylic-based rubber powders, core-shell-based rubber powders, siliconecomposite powders, silicone resin powders, and silicone rubber powders).In the resin composition in this embodiment, one inorganic filler (D)may be used alone, or two or more inorganic fillers (D) may be usedtogether in any combination and ratio.

Among these, as the inorganic filler (D), one or two or more selectedfrom the group consisting of silica, aluminum hydroxide, alumina,boehmite, magnesium oxide, and magnesium hydroxide are preferred. Byusing such an inorganic filler (D), the low thermal expansion and theflame resistance tend to be further improved.

Particularly, from the viewpoint of low thermal expansion properties, asthe inorganic filler (D), silica is preferred, and fused silica isparticularly preferred. Specific examples of the silica includeSFP-130MC manufactured by DENKI KAGAKU KOGYO KABUSHIKI KAISHA, andSC2050-MB, SC2500-SQ, and SC4500-SQ manufactured by Admatechs CompanyLimited.

In addition, as the inorganic filler (D), magnesium hydroxide and/ormagnesium oxide are also preferably used singly or in combination withanother inorganic filler such as silica. By using magnesium hydroxideand magnesium hydroxide, the flame resistance tends to be furtherimproved. Specific examples of the magnesium hydroxide include “ECOMAGZ-10” and “ECOMAG PZ-1” manufactured by Tateho Chemical Industries Co.,Ltd., “Magseeds N,” “Magseeds S,” “Magseeds EP,” and “Magseeds EP2-A”manufactured by Konoshima Chemical Co., Ltd., MGZ-1, MGZ-3, and MGZ-6Rmanufactured by Sakai Chemical Industry Co., Ltd., and “KISUMA 5,”“KISUMA 5A,” and “KISUMA 5P” manufactured by Kyowa Chemical IndustryCo., Ltd. Specific examples of the magnesium oxide include FNM-Gmanufactured by Tateho Chemical Industries Co., Ltd., and SMO, SMO-0.1,and SMO-S-0.5 manufactured by Sakai Chemical Industry Co., Ltd.

The average particle diameter of the inorganic filler (D) is notparticularly limited but is preferably 0.01 to 5.0 μm, more preferably0.1 to 2.0 μm, and further preferably 0.2 to 1.5 μm from the viewpointof prepreg productivity improvement. The “average particle diameter” ofthe inorganic filler (D) means the median diameter of the inorganicfiller (D) herein. Here, the “median diameter” means a particle diametersuch that when the particle size distribution of a powder is dividedinto two based on a certain particle diameter, the volume of particleson the larger particle diameter side and the volume on the smallerparticle diameter side each account for 50% of the whole powder. Theaverage particle diameter (median diameter) of the inorganic filler (D)can be measured by a wet laser diffraction-scattering method.

The content of the inorganic filler (D) in the resin composition is notparticularly limited but is preferably 50 to 300% by mass, morepreferably 60 to 280% by mass, and further preferably 70 to 250% by massbased on 100% by mass of the total content of the epoxy compound (A),the cyanate compound (B), and the maleimide compound (C) from theviewpoint of obtaining high plating peel strength while reducing thethermal expansion of the insulating layer. When two or more inorganicfillers (D) are used together, the total content of these preferablysatisfies the above ratios.

[I-5. Imidazole Silane (E)]

The imidazole silane (E) contained in the resin composition in thisembodiment comprises a compound represented by the following formula(3). By using an imidazole silane forming a salt with an acetate ion ora phthalate ion as represented by the following formula (3), the varnishgel time is relatively long, and the prepreg productivity is furtherimproved.

wherein R⁵ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R⁶ represents hydrogen, a vinyl group, or an alkyl group having 1to 5 carbon atoms, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 3 carbon atoms, X represents an acetate ion or a phthalateion, Y represents hydrogen or a hydroxyl group, and n represents aninteger of 1 to 3.

For R⁵, hydrogen, methyl, ethyl, undecyl, and heptadecyl are preferredparticularly in terms of the ease of synthesis. In addition, for R⁶,hydrogen, methyl, ethyl, and vinyl are preferred particularly in termsof the ease of synthesis. Further, for R⁷, methyl and ethyl arepreferred particularly in terms of the ease of synthesis, and an ethylgroup is more preferred in terms of storage stability. For R⁸, a methylgroup is preferred particularly in terms of the ease of synthesis.

The method for synthesizing the compound represented by the aboveformula (3) is not particularly limited. Examples thereof include amethod disclosed in Japanese Patent Laid-Open No. 05-186479 or JapanesePatent Laid-Open No. 09-296135. Specific examples of the imidazolesilane (E) include “IA-100A,” “IA-100F,” and “IM-100F” manufactured byJX NIPPON MINING & METALS CORP.

In the resin composition, the imidazole silane (E) is preferably in astate of being liberated from the inorganic filler (D) without beingsubjected to surface treatment for the inorganic filler (D). By being insuch a state, the adhesiveness between the insulating layer formed usingthe resin composition and the conductor layer formed on the surface ofthe insulating layer by plating tends to be further improved. From sucha viewpoint, the imidazole silane (E) is preferably directly added tothe resin composition rather than being added by a method of allowingdehydration condensation to proceed such as a dry method, a wet method,or heating and refluxing treatment.

The content of the imidazole silane (E) in the resin composition is notparticularly limited but is preferably 0.05 to 3.0% by mass, morepreferably 0.07 to 2.0% by mass, and further preferably 0.1 to 1.0% bymass based on 100% by mass of the total content of the epoxy compound(A), the cyanate compound (B), and the maleimide compound (C) from theviewpoint of prepreg productivity. When two or more imidazole silanes(E) are used together, the total content of these preferably satisfiesthe above ratios.

[I-6. Other Components]

The resin composition in this embodiment may contain one or two or moreother components in addition to the epoxy compound (A), the cyanatecompound (B), the maleimide compound (C), the inorganic filler (D), andthe imidazole silane (E).

For example, the resin composition in this embodiment may contain asilane coupling agent for the purpose of heat resistance after moistureabsorption improvement. The silane coupling agent is not particularlylimited as long as it is a silane coupling agent generally used for thesurface treatment of inorganic matter. Specific examples includeaminosilane-based silane coupling agents (for example,γ-aminopropyltriethoxysilane andN-β-(aminoethyl)-γ-aminopropyltrimethoxysilane), epoxysilane-basedsilane coupling agents (for example, γ-glycidoxypropyltrimethoxysilane),vinylsilane-based silane coupling agents (for example,γ-methacryloxypropyltrimethoxysilane), cationic silane-based silanecoupling agents (for example,N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilanehydrochloride), and phenylsilane-based silane coupling agents. One ofthese silane coupling agents may be used alone, or two or more of thesesilane coupling agents may be used together in any combination andratio.

When the silane coupling agent is used, its content is not particularlylimited but is preferably 0.050 to 5.0% by mass, more preferably 0.10 to3.0% by mass, based on 100% by mass of the inorganic filler (D) from theviewpoint of heat resistance after moisture absorption improvement. Whentwo or more silane coupling agents are used together, the total contentof these preferably satisfies the above ratios.

In addition, the resin composition in this embodiment may contain a wetdispersant for the purpose of prepreg productivity improvement and thelike. The wet dispersant is not particularly limited as long as it is awet dispersant generally used for a paint or the like. Specific examplesinclude Disperbyk-110, Disperbyk-111, Disperbyk-180, Disperbyk-161,BYK-W996, BYK-W9010, and BYK-W903 manufactured by BYK Japan KK. One ofthese wet dispersants may be used alone, or two or more of these wetdispersants may be used together in any combination and ratio.

When the wet dispersant is used, its content is not particularly limitedbut is preferably 0.10 to 5.0% by mass, more preferably 0.50 to 3.0% bymass, based on 100% by mass of the inorganic filler (D) from theviewpoint of prepreg productivity improvement. When two or more wetdispersants are used together, the total content of these preferablysatisfies the above ratios.

In addition, the resin composition in this embodiment may contain acuring accelerator for the purpose of the adjustment of the curing rateand the like. The curing accelerator is not particularly limited as longas it is known as a curing accelerator for an epoxy compound, a cyanatecompound, or the like and generally used. Specific examples includeorganometallic salts comprising a metal such as copper, zinc, cobalt,nickel, or manganese (for example, zinc octylate, cobalt naphthenate,nickel octylate, and manganese octylate), imidazoles and derivativesthereof (for example, 2-ethyl-4-methylimidazole,1-benzyl-2-phenylimidazole, and 2,4,5-triphenylimidazole), and tertiaryamines (for example, triethylamine and tributylamine). One of thesecuring accelerators may be used alone, or two or more of these curingaccelerators may be used together in any combination and ratio.

When the curing accelerator is used, its content is not particularlylimited but is preferably 0.010 to 2.0% by mass, more preferably 0.10 to1.0% by mass, based on 100% by mass of the total content of the epoxycompound (A), the cyanate compound (B), and the maleimide compound (C)from the viewpoint of obtaining high glass transition temperature. Whentwo or more curing accelerators are used together, the total content ofthese preferably satisfies the above ratios.

In addition, the resin composition in this embodiment may contain avariety of other polymer compounds and/or flame-retardant compounds andthe like in a range in which the expected properties are not impaired.The polymer compounds and the flame-retardant compounds are not limitedas long as they are generally used. The polymer compounds are notparticularly limited. Examples thereof include various thermosettingresins and thermoplastic resins and oligomers thereof, and elastomers.

The flame-retardant compounds are not particularly limited. Examplesthereof include phosphorus-containing compounds (for example,phosphates, melamine phosphate, and phosphorus-containing epoxy resins),nitrogen-containing compounds (for example, melamine andbenzoguanamine), oxazine ring-containing compounds, and silicone-basedcompounds. One of these polymer compounds and/or flame-retardantcompounds may be used alone, or two or more of these polymer compoundsand/or flame-retardant compounds may be used together in any combinationand ratio.

In addition, the resin composition in this embodiment may containvarious additives for a variety of purposes in a range in which theexpected properties are not impaired. The additives are not particularlylimited. Examples thereof include ultraviolet absorbing agents,antioxidants, photopolymerization initiators, fluorescent brighteningagents, photosensitizers, dyes, pigments, thickening agents, lubricants,defoaming agents, dispersing agents, leveling agents, and brighteningagents. One of these additives may be used alone, or two or more ofthese additives may be used together in any combination and ratio.

[I-7. Method for Producing Resin Composition]

The resin composition in this embodiment can be produced by mixing theabove-described components, that is, the epoxy compound (A), the cyanatecompound (B), the maleimide compound (C), the inorganic filler (D), theimidazole silane (E), and other components as required. The abovecomponents may be mixed in a state of a solution of the above componentsdissolved in an organic solvent, as required. The solution of the resincomposition obtained in this manner can be preferably used as a varnishwhen a prepreg and a resin sheet in this embodiment described later aremade.

The organic solvent is not limited as long as the above components caneach be preferably dissolved or dispersed, and the expected effects ofthe resin composition in this embodiment are not impaired. Specificexamples include alcohols (methanol, ethanol, and propanol), ketones(for example, acetone, methyl ethyl ketone, and methyl isobutyl ketone),amides (for example, dimethylacetamide and dimethylformamide), andaromatic hydrocarbons (for example, toluene and xylene). One of theseorganic solvents may be used alone, or two or more of these organicsolvents may be used together in any combination and ratio.

The resin composition in this embodiment has excellent prepregproductivity and excellent adhesiveness between an insulating layer anda plating conductor layer when used as a material of the insulatinglayer of a printed wiring board. Further, an insulating layer havinghigh glass transition temperature and further also having excellent heatresistance after moisture absorption can be provided. In addition, otherpreferred effects such as excellent chemical resistance can also beexhibited. In this manner, the resin composition in this embodiment hasvarious excellent characteristics and can particularly achieve bothexcellent adhesiveness and high heat resistance at high levels andtherefore is extremely useful as a material of the insulating layer of aprinted wiring board.

[II. Prepreg, Resin Sheet, Metal Foil-Clad Laminate, and Printed WiringBoard]

The prepreg, resin sheet, metal foil-clad laminate, and printed wiringboard in this embodiment are all formed using the resin composition inthis embodiment described above.

[II-1. Prepreg]

The prepreg in this embodiment is a substrate impregnated with the aboveresin composition. As the substrate, known substrates generally used asmaterials of various printed wiring boards can be used. Specificexamples thereof include glass fibers (for example, A glass, C glass, Eglass, D glass, H glass, L glass, S glass, NE glass, T glass, Q glass,UN glass, and spherical glass), inorganic fibers (for example, inorganicfibers other than glass, such as quartz), and organic fibers (forexample, polyamide-based resin fibers such as polyamide resin fibers,aromatic polyamide resin fibers, and wholly aromatic polyamide resinfibers; polyester-based resin fibers such as polyester resin fibers,aromatic polyester resin fibers, and wholly aromatic polyester resinfibers; polyimide resin fibers; and fluororesin fibers). The substratecan be appropriately selected depending on the intended application andperformance.

The shape of the substrate is not particularly limited. Examples thereofinclude woven fabrics, nonwoven fabrics, rovings, chopped strand mats,and surfacing mats. Among these, glass fibers are preferred in terms ofstrength and water absorbency, and liquid crystal polyester wovenfabrics are preferred in terms of electrical properties. Substrates canbe used singly, or in combinations of two or more.

The thickness of the substrate is not limited but is preferably, forexample, in the range of 0.01 to 0.3 mm. In terms of heat resistanceafter moisture absorption, glass woven fabrics subjected to surfacetreatment with a silane coupling agent for epoxysilane treatment,aminosilane treatment, or the like are preferred, and in terms ofdimensional stability, woven fabrics subjected to ultra-openingtreatment or clogging treatment are preferred.

The method for producing a prepreg by combining the resin compositionwith the above-described substrate is not particularly limited. Examplesthereof include a method of impregnating or coating the substrate with asolution or dispersion of the resin composition dissolved or dispersedin an organic solvent (varnish) and heating the impregnated or coatedsubstrate (for example, heating the impregnated or coated substrate in adryer at 100 to 200° C. for 1 to 60 minutes) and/or drying theimpregnated or coated substrate under reduced pressure to remove thesolvent and semi-cure the resin composition to impregnate the substratewith the resin composition.

The amount of the resin composition with which the substrate isimpregnated is preferably 15 to 95% by mass, more preferably 20 to 90%by mass, based on 100% by mass of the entire prepreg.

The prepreg in this embodiment can be used as a buildup material of aprinted wiring board. Here, the “buildup” means making a printed wiringboard having a multilayer structure by laminating prepregs or resinsheets and repeating hole making processing, wiring formation, and thelike for each layer. In a printed wiring board formed using the prepregin this embodiment, the prepreg constitutes the insulating layer. Theprinted wiring board will be described later.

[II-2. Resin Sheet]

The resin sheet in this embodiment comprises an outer layer comprisingmetal foil or a metal film, and a layer comprising the above resincomposition laminated on the outer layer.

The metal foil or the metal film used as the outer layer is notparticularly limited. Examples thereof include foil or films comprisinga metal such as copper or aluminum. Among them, copper foil or copperfilms are preferred, and particularly, electrolytic copper foil, rolledcopper foil, copper alloy films, and the like can be preferably used.The metal foil or the metal film may be subjected to known surfacetreatment, for example, nickel treatment or cobalt treatment. Thethickness of the metal foil or the metal film can be appropriatelyadjusted depending on the use application and is preferably 5 to 70 μm.

The method for producing a resin sheet by forming a layer comprising theresin composition (resin composition layer) on an outer layer comprisingthe above-described metal foil or metal film is not particularlylimited. Examples thereof include a method of applying (coating,impregnating, or the like), onto a surface of the above-described metalfoil or film, a solution of the resin composition dissolved or dispersedin an organic solvent (varnish) and heating the painted metal foil orfilm and/or drying the painted metal foil or film under reduced pressureto remove the solvent and solidify the resin composition to form a resincomposition layer.

The drying conditions are not particularly limited, but drying isperformed so that the content of the organic solvent in the resincomposition layer is preferably 10 parts by mass or less, morepreferably 5.0 parts by mass or less, based on 100 parts by mass of theresin composition layer. The conditions that achieve such drying arealso different depending on the amount of the organic solvent in thevarnish, and, for example, in the case of a varnish comprising 30 to 60parts by mass of an organic solvent, drying should be performed underthe heating condition of 50 to 160° C. for about 3 to 10 minutes. Thethickness of the resin composition layer in the resin sheet in thisembodiment is not limited but is usually similar to the thickness of theouter layer (generally about 5 to 70 μm as described above), preferably10 to 100 μm.

The resin sheet in this embodiment can also be used as a buildupmaterial of a printed wiring board. In a printed wiring board formedusing the resin sheet in this embodiment, the layer comprising the resincomposition constitutes the insulating layer. The printed wiring boardwill be described later.

[II-3. Metal Foil-Clad Laminate]

The metal foil-clad laminate in this embodiment comprises the aboveprepreg and metal foil laminated on one surface or both surfaces of theprepreg. One prepreg may be used, or two or more prepregs may belaminated and used.

The method for making the metal foil-clad laminate in this embodiment isnot limited. Examples thereof include a method of disposing metal foilon one surface or both surfaces of one prepreg or a laminate afterlaminating two or more prepregs, and performing laminate molding underconditions, for example, a temperature of 180 to 220° C., a heating timeof 100 to 300 minutes, and a surface pressure of 20 to 40 kgf/cm² (about2.0 MPa to about 3.9 MPa).

The metal foil is not particularly limited. Examples thereof includefoil of metals such as copper and aluminum. Among these, copper foil ispreferred. Particularly, electrolytic copper foil, rolled copper foil,and the like can be preferably used. The metal foil may be subjected toknown surface treatment, for example, nickel treatment or cobalttreatment. The thickness of the metal foil can be appropriately adjustedin a range suitable as a material of a printed wiring board and ispreferably 2 to 35 μm.

In addition, from the viewpoint of transferring the matte surface of themetal foil to the surface of the insulating layer (the layer comprisingthe prepreg) to increase adhesion to a conductor layer formed on theinsulating layer by plating by the anchor effect of the irregularitiestransferred to the insulating layer surface, the surface roughness Rz ofthe matte surface of the metal foil is preferably 0.5 to 2.5 μm, morepreferably 0.6 to 2.3 μm, and further preferably 0.7 to 2.0 μm. Here,the “surface roughness Rz” is an indicator representing the roughness ofthe matte surface of the metal foil and can be obtained by measuring bya laser microscope the roughness curve of a surface to be measured,extracting five peaks exceeding the average line in descending order andfive valleys not reaching the average line in ascending order, andcalculating the average value of the absolute values of the heights ofthe extracted peaks and the depths of the extracted valleys.

The metal foil-clad laminate in this embodiment can also be used as abuildup material of a printed wiring board. In a printed wiring boardformed using the metal foil-clad laminate in this embodiment, theprepreg (the substrate and the resin composition with which thesubstrate is impregnated) constitutes the insulating layer. The printedwiring board will be described later.

[II-4. Printed Wiring Board]

The printed wiring board in this embodiment comprises an insulatinglayer and a conductor layer formed on the surface of the insulatinglayer, and the insulating layer comprises the above resin composition.

Such a printed wiring board can be made using as a buildup material theprepreg, the resin sheet, or the metal foil-clad laminate in thisembodiment described above. In other words, by making a printed wiringboard using these as a buildup material, the prepreg (the substrate andthe resin composition with which the substrate is impregnated) or theresin composition layer (the layer comprising the resin composition) ofthe resin sheet constitutes the insulating layer comprising the resincomposition.

Specifically, when the resin sheet in this embodiment is used as abuildup material, the printed wiring board in this embodiment isobtained by surface-treating the resin composition layer (insulatinglayer) of the resin sheet and forming a wiring pattern (conductor layer)on the insulating layer surface by plating according to an ordinarymethod.

When the metal foil-clad laminate in this embodiment is used as abuildup material, the printed wiring board in this embodiment can beobtained by etching the metal foil of the metal foil-clad laminate, thensurface-treating the layer comprising the prepreg (insulating layer),and forming a wiring pattern (conductor layer) on the insulating layersurface by plating according to an ordinary method.

When the prepreg in this embodiment is used as a buildup material, theprinted wiring board in this embodiment can be obtained by the abovemethod after a metal foil-clad laminate is made using the prepreg by theabove method for producing a metal foil-clad laminate.

Alternatively, when the prepreg in this embodiment is used as a materialof a multilayer printed wiring board as described later or the like, theprepreg may be used as a buildup material as it is.

In all cases, other various steps (for example, hole drilling forforming via holes, through holes, and the like) may be added asrequired.

Steps for producing the printed wiring board in this embodiment will bedescribed below.

The hole drilling is carried out for the formation of via holes, throughholes, and the like. The hole drilling is performed by using any one ofknown methods such as an NC drill, a carbonic acid gas laser, a UVlaser, a YAG laser, and plasma or combining two or more as required.

The surface treatment for the insulating layer is carried out from theviewpoint of an improvement in the adhesiveness between the insulatinglayer and the plating conductor layer, smear removal, and the like. Thesurface treatment is not particularly limited. Examples thereof includeroughening treatment and silane coupling treatment. The rougheningtreatment can also serve as the removal of smears produced by the holemaking step. In this case, the roughened state is different depending onthe difference in the degree of cure of the resin composition, andtherefore for the conditions of laminate molding described later,optimal conditions are preferably selected in combination withsubsequent roughening treatment conditions and plating conditions.

The roughening treatment comprises a swelling step, a surface rougheningand smear dissolving step, and a neutralization step.

The swelling step is performed by swelling the surface insulating layerusing a swelling agent. The swelling agent is not particularly limitedas long as the wettability of the surface insulating layer is improved,and the surface insulating layer can be swollen to the extent thatoxidative decomposition is accelerated in the next surface rougheningand smear dissolving step. Examples of the swelling agent include alkalisolutions and surfactant solutions.

The surface roughening and smear dissolving step is performed using anoxidant. The oxidant is not particularly limited. Examples thereofinclude permanganate solutions. Preferred specific examples includepotassium permanganate aqueous solutions and sodium permanganate aqueoussolutions. Such oxidant treatment is referred to as wet desmear, and inaddition to the wet desmear, other known roughening treatment such asdry desmear by plasma treatment or UV treatment, mechanical polishing bya buff or the like, and sandblast may be appropriately combined andcarried out.

The neutralization step neutralizes the oxidant used in the previousstep with a reducing agent. The reducing agent is not particularlylimited. Examples thereof include amine-based reducing agents. Amongthese, examples of the reducing agent include acidic reducing agentssuch as hydroxylamine sulfate aqueous solutions, ethylenediaminetetraacetic acid aqueous solutions, and nitrilotriacetic acid aqueoussolutions.

When a fine wiring pattern is formed, the surface irregularities of theinsulating layer after roughening treatment are preferably small.Specifically, the Rz value is preferably 4.0 μm or less, more preferably2.0 μm or less. The surface irregularities after roughening treatmentare determined according to the degree of cure of the resin composition,the conditions of roughening treatment, and the like, and thereforeoptimal conditions for obtaining the desired surface irregularities arepreferably selected. Particularly, the insulating layer comprising theresin composition in this embodiment can ensure adhesiveness to theplating conductor layer even if the surface roughness is low, and thisinsulating layer is extremely preferred.

Examples of the method for forming a wiring pattern (conductor layer) byplating include a semi-additive method, a full additive method, and asubtractive method. Among them, the semi-additive method is preferredfrom the viewpoint of forming a fine wiring pattern.

Examples of the method for forming a pattern by the semi-additive methodinclude a method for forming a wiring pattern by forming a thinconductor layer on an insulating layer surface by electroless plating orthe like, then selectively providing electrolytic plating (patternplating) using a plating resist, then stripping the plating resist, andetching an appropriate amount of the whole.

Examples of the method for forming a pattern by the full additive methodinclude a method for forming a wiring pattern by previously performingpattern formation on an insulating layer surface using a plating resist,and selectively attaching electroless plating or the like.

Examples of the method for forming a pattern by the subtractive methodinclude a method for forming a wiring pattern by forming a conductorlayer on an insulating layer surface by plating and then selectivelyremoving the conductor layer using an etching resist.

When a wiring pattern is formed by plating, drying is preferablyperformed after the plating from the viewpoint of improving the adhesionstrength between the insulating layer and the conductor layer. Inpattern formation by the semi-additive method, electroless plating andelectrolytic plating are performed in combination, and at this time,drying is preferably performed after the electroless plating and afterthe electrolytic plating. The drying after the electroless plating ispreferably performed, for example, at 80 to 180° C. over 10 to 120minutes, and the drying after the electrolytic plating is preferablyperformed, for example, at 130 to 220° C. over 10 to 120 minutes.

The printed wiring board in this embodiment can also be a multilayerprinted wiring board. For example, a metal foil-clad laminate in whichmetal foil (for example, copper or aluminum) is disposed on bothsurfaces of a prepreg is formed by the above procedure, and then innerlayer circuits are formed in the metal foil-clad laminate, and theobtained circuits are subjected to blackening treatment to provide aninner layer circuit board. By repeating the operation of disposing aprepreg or a resin sheet on one surface or both surfaces of the innerlayer circuit board obtained in this manner or metal foil (for example,copper or aluminum) and further disposing metal foil (for example,copper or aluminum) or a release film (a film obtained by coating asurface of a polyethylene film, a polypropylene film, a polycarbonatefilm, a polyethylene terephthalate film, an ethylene-tetrafluoroethylenecopolymer film, or the like with a release agent) on the outside toperform laminate molding, a multilayer printed wiring board is produced.

The laminate molding is performed by using a method generally used forthe laminate molding of an ordinary laminate for a printed wiring board,for example, a multistage press, a multistage vacuum press, a laminator,a vacuum laminator, or an autoclave molding machine, and appropriatelyselecting the temperature, for example, in the range of 100 to 300° C.,the pressure, for example, in the range of 0.1 to 100 kgf/cm² (about 9.8kPa to about 38 MPa), and the heating time, for example, in the range of30 seconds to 5 hours. In addition, post-curing may be performed, forexample, at a temperature of 150 to 300° C., as required, to adjust thedegree of cure.

EXAMPLES

This embodiment will be described in detail below by showing a SynthesisExample, Examples, and Comparative Examples, but this embodiment is notlimited to these.

1. Production of Cyanate Compound Synthesis Example 1 Synthesis ofα-Naphthol Aralkyl-Based Cyanate Compound (Compound of Formula (4a))

wherein the average value of n is 3 to 4.

A reactor to which a thermometer, a stirrer, a dropping funnel, and areflux condenser were attached was previously cooled to 0 to 5° C. witha saline solution, and the reactor was charged with 7.47 g (0.122 mol)of cyanogen chloride, 9.75 g (0.0935 mol) of 35% hydrochloric acid, 76mL of water, and 44 mL of methylene chloride.

While the temperature in this reactor was kept at −5 to +5° C. and thepH was kept at 1 or less, a solution of 20 g (0.0935 mol) of anα-naphthol aralkyl resin represented by the following formula (4a′)(SN485, OH group equivalent: 214 g/eq. softening point: 86° C.,manufactured by Nippon Steel Chemical Co., Ltd.) and 14.16 g (0.14 mol)of triethylamine dissolved in 92 mL of methylene chloride was droppedthrough the dropping funnel under stirring over 1 hour, and after thecompletion of the dropping, 4.72 g (0.047 mol) of triethylamine wasfurther dropped over 15 minutes.

wherein the average value of n is 3 to 4.

After the completion of the dropping, the mixture was stirred at thesame temperature for 15 minutes, and then the reaction liquid wasseparated to isolate the organic layer. The obtained organic layer waswashed twice with 100 mL of water, and then the methylene chloride wasdistilled off by an evaporator under reduced pressure, and finally theresidue was concentrated to dryness at 80° C. for 1 hour to obtain 23.5g of a cyanate compound of an α-naphthol aralkyl resin (α-naphtholaralkyl-based cyanate compound) represented by the above formula (4a).

2. Making of Resin Compositions and Copper-Clad Laminates Example 1

53.3 Parts by mass (40 parts by mass in terms of nonvolatile matter) ofa methyl ethyl ketone solution (hereinafter also referred to as a “MEKsolution”) of a biphenyl aralkyl-based epoxy compound represented by theabove formula (6) (NC-3000-FH, epoxy equivalent: 320 g/eq., manufacturedby Nippon Kayaku Co., Ltd.) (75% by mass of nonvolatile matter) as anepoxy compound (A), further 20 parts by mass (10 parts by mass in termsof nonvolatile matter) of a MEK solution of a naphthalene-based epoxycompound (HP4710, epoxy equivalent of 240 g/eq., manufactured by DICCorporation) (50% by mass of nonvolatile matter) as a second epoxycompound (A), 70 parts by mass (35 parts by mass in terms of nonvolatilematter) of a methyl ethyl ketone solution of the α-naphtholaralkyl-based cyanate compound of the above formula (4a) obtained bySynthesis Example 1 (cyanate equivalent: 261 g/eq.) (50% by mass ofnonvolatile matter) as a cyanate compound (B), 30 parts by mass (15parts by mass in terms of nonvolatile matter) of a MEK solution of amaleimide compound represented by the above formula (2) (BMI-2300,manufactured by Daiwa Fine Chemicals Co., Ltd.) (50% by mass ofnonvolatile matter) as a maleimide compound (C), 0.5 parts by mass (0.35parts by mass in terms of nonvolatile matter) of an imidazole silane inwhich X in the above formula (3) was an acetate ion and Y was a hydroxylgroup (IA-100A (70% by mass of nonvolatile matter), manufactured by JXNIPPON MINING & METALS CORP.) as an imidazole silane (E), and 50 partsby mass (0.5 parts by mass in terms of nonvolatile matter) of apropylene glycol monomethyl ether acetate solution of2,4,5-triphenylimidazole (manufactured by Wako Pure Chemical Industries,Ltd.) (1% by mass of nonvolatile matter) and 5 parts by mass (0.05 partsby mass in terms of nonvolatile matter) of a MEK solution of manganeseoctylate (1% by mass of nonvolatile matter) as curing accelerators weredissolved or dispersed in MEK. Further, 100 parts by mass of silica(SFP-130MC, manufactured by DENKI KAGAKU KOGYO KABUSHIKI KAISHA, averageparticle diameter of 0.6 μm) as an inorganic filler (D) was added, andthe mixture was stirred using a high speed stirring apparatus for 30minutes to obtain a varnish (a solution of a resin compositioncomprising the epoxy compounds (A), the cyanate compound (B), themaleimide compound (C), the inorganic filler (D), and the imidazolesilane (E)).

This varnish was further diluted with MEK, and an E-glass woven fabrichaving a thickness of 0.1 mm was impregnated with the diluted varnishand heated and dried at 160° C. for 4 minutes to obtain a prepreg havinga resin composition content of 50% by mass. Four or eight of theobtained prepregs were stacked, and the matte surface of 3 μm thickelectrolytic copper foil (JXUT-I, manufactured by JX NIPPON MINING &METALS CORP., surface roughness Rz=1.1 μm) was disposed on the prepregside. Laminate molding was performed at a pressure of 40 kgf/cm² (about3.9 MPa) and a temperature of 220° C. for 120 minutes to obtaincopper-clad laminates having insulating layer thicknesses of 0.4 mm and0.8 mm (using four and eight prepregs, respectively).

Example 2

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that the amount of the imidazole silane in which X inthe above formula (3) was an acetate ion and Y was a hydroxyl group(IA-100A) used as the imidazole silane (E) was changed to 3 parts bymass (2.1 parts by mass in terms of nonvolatile matter).

Example 3

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that 30 parts by mass (15 parts by mass in terms ofnonvolatile matter) of a MEK solution of a maleimide compoundrepresented by the above formula (1) (BMI-1000P, manufactured by K.IChemical Industry Co., Ltd.) (50% by mass of nonvolatile matter) insteadof the maleimide compound represented by the above formula (2)(BMI-2300) was used as the maleimide compound (C).

Example 4

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that the use amount of the MEK solution of themaleimide compound represented by the above formula (2) (BMI-2300) (50%by mass of nonvolatile matter) was changed to 16 parts by mass (8 partsby mass in terms of nonvolatile matter), and 14 parts by mass (7 partsby mass in terms of nonvolatile matter) of a MEK solution of themaleimide compound represented by the above formula (1) (BMI-1000P) (50%by mass of nonvolatile matter) as a second maleimide compound (C) wasfurther added.

Example 5

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that the use amount of the MEK solution of the biphenylaralkyl-based epoxy compound represented by the above formula (6)(NC-3000-FH) (75% by mass of nonvolatile matter), the epoxy compound(A), was changed to 60 parts by mass (45 parts by mass in terms ofnonvolatile matter), the amount of the MEK solution of the α-naphtholaralkyl-based cyanate compound of the above formula (4a) obtained bySynthesis Example 1 (50% by mass of nonvolatile matter) used as thecyanate compound (B) was changed to 40 parts by mass (20 parts by massin terms of nonvolatile matter), the use amount of the MEK solution ofthe maleimide compound represented by the above formula (2) (BMI-2300)(50% by mass of nonvolatile matter), the maleimide compound (C), waschanged to 40 parts by mass (20 parts by mass in terms of nonvolatilematter), the use amount of the imidazole silane in which X in the aboveformula (3) was an acetate ion and Y was a hydroxyl group (IA-100A), theimidazole silane (E), was changed to 1 part by mass (0.7 parts by massin terms of nonvolatile matter), 10 parts by mass (5 parts by mass interms of nonvolatile matter) of a MEK solution of the maleimide compoundrepresented by the above formula (1) (BMI-1000P) (50% by mass ofnonvolatile matter) as a second maleimide compound (C) was furtheradded, and 50 parts by mass of silica (SC4500-SQ, manufactured byAdmatechs Company Limited, average particle diameter of 1.5 μm) as asecond inorganic filler (D) was further added.

Example 6

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 5 except that the use amount of the silica (SC4500-SQ), thesecond inorganic filler (D), was changed to 200 parts by mass, and theuse amount of the imidazole silane in which X in the above formula (3)was an acetate ion and Y was a hydroxyl group (IA-100A), an imidazolesilane, was changed to 0.2 parts by mass (0.14 parts by mass in terms ofnonvolatile matter).

Example 7

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 5 except that the use amount of the MEK solution of theα-naphthol aralkyl-based cyanate compound of the above formula (4a)obtained by Synthesis Example 1 (50% by mass of nonvolatile matter), thecyanate compound (B), was changed to 80 parts by mass (40 parts by massin terms of nonvolatile matter), the use amount of the MEK solution ofthe maleimide compound represented by the above formula (2) (BMI-2300)(50% by mass of nonvolatile matter), the maleimide compound (C), waschanged to 10 parts by mass (5 parts by mass in terms of nonvolatilematter), the maleimide compound represented by the above formula (1)(BMI-1000P), the second maleimide compound (C), was not used, and theuse amount of the imidazole silane in which X in the above formula (3)was an acetate ion and Y was a hydroxyl group (IA-100A), the imidazolesilane (E), was changed to 0.5 parts by mass (0.35 parts by mass interms of nonvolatile matter).

Example 8

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 7 except that the use amount of the MEK solution of the biphenylaralkyl-based epoxy compound represented by the above formula (6)(NC-3000-FH) (75% by mass of nonvolatile matter), the epoxy compound(A), was changed to 73.3 parts by mass (55 parts by mass in terms ofnonvolatile matter), the use amount of the MEK solution of thenaphthalene-based epoxy compound (HP4710) (50% by mass of nonvolatilematter), the second epoxy compound (A), was changed to 30 parts by mass(15 parts by mass in terms of nonvolatile matter), the use amount of theMEK solution of the α-naphthol aralkyl-based cyanate compound of theabove formula (4a) obtained by Synthesis Example 1 (50% by mass ofnonvolatile matter), the cyanate compound (B), was changed to 40 partsby mass (20 parts by mass in terms of nonvolatile matter), and the MEKsolution of the maleimide compound represented by the above formula (2)(BMI-2300) (50% by mass of nonvolatile matter), the maleimide compound(C), was changed to 20 parts by mass (10 parts by mass in terms ofnonvolatile matter).

Example 9

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 7 except that the use amount of the MEK solution of theα-naphthol aralkyl-based cyanate compound of the above formula (4a)obtained by Synthesis Example 1 (50% by mass of nonvolatile matter), thecyanate compound (B), was changed to 70 parts by mass (35 parts by massin terms of nonvolatile matter), and the use amount of the MEK solutionof the maleimide compound represented by the above formula (2)(BMI-2300) (50% by mass of nonvolatile matter), the maleimide compound(C), was changed to 20 parts by mass (10 parts by mass in terms ofnonvolatile matter).

Example 10

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 9 except that 70 parts by mass (35 parts by mass in terms ofnonvolatile matter) of a MEK solution of a cyanate compound representedby the following formula (5a) in which R^(13 to 16) in the above formula(5) were all hydrogen atoms (Primaset PT-60, manufactured by Lonza JapanLtd.,) (50% by mass of nonvolatile matter) instead of the α-naphtholaralkyl-based cyanate compound of the above formula (4a) obtained bySynthesis Example 1 was used as the cyanate compound (B).

n represents an integer of 1 or more.

Example 11

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 9 except that 0.5 parts by mass (0.35 parts by mass in terms ofnonvolatile matter) of an imidazole silane in which X in the aboveformula (3) was a phthalate ion and Y was a hydroxyl group (IA-100F,manufactured by JX NIPPON MINING & METALS CORP., 70% of nonvolatilematter) instead of the imidazole silane in which X in the above formula(3) was an acetate ion and Y was a hydroxyl group (IA-100A) was used asthe imidazole silane (E).

Example 12

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 9 except that 0.5 parts by mass (0.4 parts by mass in terms ofnonvolatile matter) of an imidazole silane in which X in the aboveformula (3) was a phthalate ion and Y was hydrogen (IM-100F,manufactured by JX NIPPON MINING & METALS CORP., 80% of nonvolatilematter) instead of the imidazole silane in which X in the above formula(3) was an acetate ion and Y was a hydroxyl group (IA-100A) was used asthe imidazole silane (E).

Example 13

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 9 except that 100 parts by mass of magnesium hydroxide (MGZ-6R,Sakai Chemical Industry Co., Ltd., average particle diameter of 2.0 μm)instead of the silica (SFP-130MC) and the silica (SC4500-SQ) as theinorganic filler (D) was blended into the varnish.

Example 14

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 13 except that 100 parts by mass of magnesium oxide (SMO-0.4,manufactured by Sakai Chemical Industry Co., Ltd., average particlediameter of 0.4 μm) instead of the magnesium hydroxide was used as theinorganic filler (D).

Example 15

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 13 except that 100 parts by mass of boehmite silica (AOH-60,manufactured by Nabaltec AG, average particle diameter of 0.9 μm)instead of the magnesium hydroxide was used as the inorganic filler (D).

Comparative Example 1

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that the imidazole silane in which X in the aboveformula (3) was an acetate ion and Y was a hydroxyl group (IA-100A) asthe imidazole silane (E) was not used.

Comparative Example 2

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that 1 part by mass (0.9 parts by mass in terms ofnonvolatile matter) of an imidazole silane represented by the followingformula (8) (IS-1000, manufactured by JX NIPPON MINING & METALS CORP.,90% by mass of nonvolatile matter) instead of the imidazole silane inwhich X in the above formula (3) was an acetate ion and Y was a hydroxylgroup (IA-100A) was used as the imidazole silane (E).

wherein R¹⁷ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R¹⁸ represents hydrogen, a vinyl group, or an alkyl group having1 to 5 carbon atoms, R¹⁹ and R²⁰ represent an alkyl group having 1 to 3carbon atoms, and n represents an integer of 1 to 3.

Comparative Example 3

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that 1 part by mass (0.95 parts by mass in terms ofnonvolatile matter) of an imidazole silane represented by the followingformula (9) (IM-1000, manufactured by JX NIPPON MINING & METALS CORP.,95% by mass of nonvolatile matter) instead of the imidazole silane inwhich X in the above formula (3) was an acetate ion and Y was a hydroxylgroup (IA-100A) was used as the imidazole silane (E).

wherein R²¹ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R²² represents hydrogen, a vinyl group, or an alkyl group having1 to 5 carbon atoms, R²³ and R²⁴ represent an alkyl group having 1 to 3carbon atoms, and n represents an integer of 1 to 3.

Comparative Example 4

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that 30 parts by mass (15 parts by mass in terms ofnonvolatile matter) of a MEK solution of bis(3-ethyl-5-methyl-4maleimidophenyl)methane (BMI-70, manufactured by K.I Chemical IndustryCo., Ltd.) (50% by mass of nonvolatile matter) instead of the maleimidecompound represented by the above formula (2) (BMI-2300) was used as themaleimide compound (C).

Comparative Example 5

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 1 except that 70 parts by mass (35 parts by mass in terms ofnonvolatile matter) of a MEK solution of a naphthol aralkyl-basedphenolic resin (SN495V2 (SN-OH), phenol equivalent of 236 g/eq.,manufactured by Nippon Steel Chemical Co., Ltd.) (50% by mass ofnonvolatile matter) instead of the α-naphthol aralkyl-based cyanatecompound of the above formula (4a) obtained by Synthesis Example 1 wasused.

Comparative Example 6

A varnish (a solution of a resin composition) was prepared andcopper-clad laminates (metal foil-clad laminates) were obtained as inExample 9 except that the use amount of the MEK solution of the biphenylaralkyl-based epoxy compound represented by the above formula (6)(NC-3000-FH) (75% by mass of nonvolatile matter), the epoxy compound(A), was changed to 35.7 parts by mass (25 parts by mass in terms ofnonvolatile matter), the amount of the MEK solution of thenaphthalene-based epoxy compound (HP4710) (50% by mass of nonvolatilematter), the second epoxy compound (A), used was further changed to 10parts by mass (5 parts by mass in terms of nonvolatile matter), and theuse amount of the MEK solution of the maleimide compound represented bythe above formula (2) (BMI-2300) (50% by mass of nonvolatile matter),the maleimide compound (C), was changed to 70 parts by mass (35 parts bymass in terms of nonvolatile matter).

3. Evaluation of Resin Compositions Wet Roughening Treatment ofCopper-Clad Laminates and Conductor Layer Plating:

The surface layer copper foil of the copper-clad laminates havinginsulating layer thicknesses of 0.4 mm and 0.8 mm (using four and eightprepregs, respectively) obtained in Examples 1 to 15 and ComparativeExamples 1 to 6 was removed by etching. Electroless copper plating ofabout 0.5 μm was provided by the process of electroless copper platingmanufactured by C. Uyemura & Co., Ltd. (names of chemical solutionsused: MCD-PL, MDP-2, MAT-SP, MAB-4-C, MEL-3-APEA ver. 2), and drying wasperformed at 130° C. for 1 hour. Next, electrolytic copper plating wasprovided so that the thickness of plating copper was 18 μm, and dryingwas performed at 180° C. for 1 hour. In this manner, circuit wiringboard samples in which conductor layers (plating copper) having athickness of 18 μm were formed on insulating layers having thicknessesof 0.4 mm and 0.8 mm were made and subjected to the followingevaluation.

Evaluation Methods: (1) Rate of Change in Varnish Gel Time

A varnish was placed on a hot plate at 170° C., and the time until thevarnish cured (varnish gel time) was measured. The varnish gel time onthe day of varnish making and the varnish gel time when the varnish wasstored at 30° C. for 2 days were measured. The amount of change invarnish gel time was obtained by numerical formula (1) below andevaluated according to the following evaluation criteria. The resultsare shown in Tables 1 to 3.

the amount of change in varnish gel time (%)=varnish gel time 2 daysafter varnish making/varnish gel time on the day of varnishmaking×100.  Numerical formula (1):

Good: the amount of change in varnish gel time was 75% to 100%.

Fair: the amount of change in varnish gel time was 50% to 74%.

Poor: the amount of change in varnish gel time was 49% or less.

(2) Plating Copper Peel Strength:

The circuit wiring board samples having an insulating layer thickness of0.4 mm made by the above procedure were used. The plating copper peelstrength (adhesive force) was measured three times according toJISC6481, and the average value of the plating copper peel strength wasobtained. For the samples swollen by the drying after the electrolyticcopper plating, evaluation was performed using the portion not swollen.The results are shown in Tables 1 to 3.

(3) Glass Transition Temperature:

The circuit wiring board samples having an insulating layer thickness of0.8 mm made by the above procedure were used. The surface layer copperfoil of the circuit wiring board sample was removed by etching. Thetemperature was increased by 10° C. per minute from 40° C. to 300° C. bya thermomechanical analysis apparatus (Q800 manufactured by TAInstruments), and the glass transition temperature was measured. Theresults are shown in Tables 1 to 3.

(4) Heat Resistance after Moisture Absorption:

The circuit wiring board samples having an insulating layer thickness of0.4 mm made by the above procedure were used. The circuit wiring boardsample was cut into a 50 mm×50 mm square, and then the plating copperexcept half of the plating copper on one surface was removed by etchingto make a sample. The sample was treated at 121° C. and 2 atmospheres bya pressure cooker tester (PC-3 model manufactured by HIRAYAMAMANUFACTURING CORPORATION) for 1, 3, and 5 hours and then immersed in asolder bath at 260° C. for 60 seconds, and the presence or absence ofabnormality in appearance change was visually observed. Three sampleswere tested, and for each sample, one without abnormality was describedas “Good,” and one in which swelling occurred was described as “No.” Theresults are shown in Tables 1 to 3. In the tables, “PCT-1H,” “PCT-3H,”and “PCT-5H” show the results obtained after the treatment by thepressure cooker tester for 1, 3, and 5 hours, respectively.

TABLE 1 Evaluation Example Example Example Example Example ExampleExample Example results 1 2 3 4 5 6 7 8 Amount of Good Fair Good GoodGood Good Good Good change in varnish gel time (%) Plating copper 0.830.85 0.9 0.85 0.82 0.78 0.75 0.9 peel strength (kg/cm) Glass transition270 270 240 255 250 250 260 240 temperature DMA (° C.) Heat PCT- GoodGood Good Good Good Good Good Good resistance 1H Good Good Good GoodGood Good Good Good after Good Good Good Good Good Good Good Goodmoisture PCT- Good Good Good Good Good Good Good Good absorption 3H GoodGood Good Good Good Good Good Good Good Good Good Good Good Good GoodGood PCT- Good Good Good Good Good Good Good Good 5H Good Good Good GoodGood Good Good Good Good Good Good Good Good Good Good Good *DMA:dynamic viscoelasticity measurement

TABLE 2 Evaluation Example Example Example Example Example ExampleExample results 9 10 11 12 13 14 15 Amount of Good Good Good Good GoodGood Good change in varnish gel time (%) Plating copper 0.8 0.7 0.8 0.810.85 0.85 0.85 peel strength (kg/cm) Glass transition 265 275 270 270270 270 270 temperature DMA (° C.) Heat PCT- Good Good Good Good GoodGood Good resistance 1H Good Good Good Good Good Good Good after GoodGood Good Good Good Good Good moisture PCT- Good Good Good Good GoodGood Good absorption 3H Good Good Good Good Good Good Good Good GoodGood Good Good Good Good PCT- Good Good Good Good Good Good Good 5H GoodGood Good Good Good Good Good Good Good Good Good Good Good Good *DMA:dynamic viscoelasticity measurement

TABLE 3 Evaluation Comparative Comparative Comparative ComparativeComparative Comparative results Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Amount of Good Poor Poor Good Good Good change invarnish gel time (%) Plating copper 0.6 0.6 0.55 0.5 0.7 0.45 peelstrength (kg/cm) Glass transition 270 270 270 270 220 285 temperatureDMA (° C.) Heat PCT- Good Good Good Good Good Good resistance 1H GoodGood Good Good Good Good after Good Good Good Good Good Good moisturePCT- Good Good Good Good Good Good absorption 3H Good Good Good GoodGood Good Good No Good Good No Good PCT- Good Good Good Good No Good 5HGood No Good Good No Good Good No Good Good No Good *DMA: dynamicviscoelasticity measurement

From Tables 1 to 3, it is seen that Examples 1 to 15 having theinsulating layers formed using the resin compositions of the presentinvention have higher plating peel strength and glass transitiontemperature and also better heat resistance after moisture absorptionthan Comparative Examples 1 to 6. In addition, in Comparative Examples 2and 3, the amount of change in varnish gel time was small, and it wasdifficult to stably produce the prepreg.

This application is based on Japanese Patent Application No. 2013-116901filed with the Japan Patent Office on Jun. 3, 2013, the contents ofwhich are incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The resin composition of the present invention exhibits various effectssuch as excellent prepreg productivity and excellent adhesivenessbetween an insulating layer and a plating conductor layer and alsoexcellent heat resistance when used as a material of the insulatinglayer of a printed wiring board as described above, and therefore theresin composition of the present invention is extremely useful as amaterial of the insulating layer of a printed wiring board.

1. A resin composition used as a material of an insulating layer of aprinted wiring board comprising the insulating layer and a conductorlayer formed on a surface of the insulating layer by plating, the resincomposition comprising: an epoxy compound (A); a cyanate compound (B); amaleimide compound (C); an inorganic filler (D); and an imidazole silane(E), wherein the maleimide compound (C) comprises a maleimide compoundrepresented by the following formula (1) and/or a maleimide compoundrepresented by the following formula (2), a content of the maleimidecompound (C) is 25% by mass or less based on 100% by mass of a totalcontent of the epoxy compound (A), the cyanate compound (B), and themaleimide compound (C), and the imidazole silane (E) comprises acompound represented by the following formula (3),

wherein n is a real number in a range of 1 to 30 as an average value,

wherein R¹, R², R³, and R⁴ each independently represent a hydrogen atomor a methyl group, and n is a real number in a range of 1 to 10 as anaverage value,

wherein R⁵ represents hydrogen or an alkyl group having 1 to 20 carbonatoms, R⁶ represents hydrogen, a vinyl group, or an alkyl group having 1to 5 carbon atoms, R⁷ and R⁸ each independently represent an alkyl grouphaving 1 to 3 carbon atoms, X represents an acetate ion or a phthalateion, Y represents hydrogen or a hydroxyl group, and n represents aninteger of 1 to
 3. 2. The resin composition according to claim 1,wherein the cyanate compound (B) comprises a naphthol aralkyl-basedcyanate compound represented by the following formula (4) and/or anovolac-based cyanate compound represented by the following formula (5),

wherein R⁹, R^(1′), R¹¹, and R¹² each independently represent a hydrogenatom or a methyl group, and n represents an integer of 1 or more,

wherein R¹³, R¹⁴, R¹⁵, and R¹⁶ each independently represent a hydrogenatom or a methyl group, and n represents an integer of 1 or more.
 3. Theresin composition according to claim 1, wherein the inorganic filler (D)comprises at least one or more selected from the group consisting ofsilica, aluminum hydroxide, alumina, boehmite, magnesium oxide, andmagnesium hydroxide.
 4. The resin composition according to claim 1,wherein a content of the epoxy compound (A) is 40 to 75% by mass basedon 100% by mass of the total content of the epoxy compound (A), thecyanate compound (B), and the maleimide compound (C).
 5. The resincomposition according to claim 1, wherein a content of the cyanatecompound (B) is 20 to 40% by mass based on 100% by mass of the totalcontent of the epoxy compound (A), the cyanate compound (B), and themaleimide compound (C).
 6. The resin composition according to claim 1,wherein a content of the inorganic filler (D) is 50 to 300% by massbased on 100% by mass of the total content of the epoxy compound (A),the cyanate compound (B), and the maleimide compound (C).
 7. The resincomposition according to claim 1, wherein a content of the imidazolesilane (E) is 0.10 to 3.0% by mass based on 100% by mass of the totalcontent of the epoxy compound (A), the cyanate compound (B), and themaleimide compound (C).
 8. A prepreg comprising a substrate and theresin composition according to claim 1 with which the substrate isimpregnated.
 9. A resin sheet comprising an outer layer comprising metalfoil or a metal film, and a layer comprising the resin compositionaccording to claim 1 laminated on the outer layer.
 10. A metal foil-cladlaminate comprising the prepreg according to claim 8 and metal foillaminated on one surface or both surfaces of the prepreg.
 11. The metalfoil-clad laminate according to claim 10, wherein the metal foil has amatte surface having a surface roughness Rz of 0.70 μm to 2.5 μm.
 12. Aprinted wiring board made using the prepreg according to claim 8 as abuildup material.
 13. A printed wiring board made using the resin sheetaccording to claim 9 as a buildup material.
 14. The printed wiring boardaccording to claim 13 made by surface-treating the layer comprising theresin composition in the resin sheet, and forming a pattern on the layercomprising the resin composition by plating.
 15. A printed wiring boardmade using the metal foil-clad laminate according to claim 10 as abuildup material.
 16. The printed wiring board according to claim 15made by etching the metal foil of the metal foil-clad laminate,surface-treating a layer comprising the prepreg in the metal foil-cladlaminate, and forming a pattern on the layer comprising the prepreg byplating.
 17. A printed wiring board comprising an insulating layer and aconductor layer formed on a surface of the insulating layer, wherein theinsulating layer comprises the resin composition according to claim 1.